Bermuda grass pollen (BGP) contains a very complex mixture of allergens, but only a few have been characterized. One of the allergens, with an apparent molecular mass of 21 kDa, has been shown to bind serum IgE from 29% of patients with BGP allergy. A combination of chromato-graphic techniques (ion exchange and reverse phase HPLC) was used to purify the 21 kDa allergen.